[Phanx]

The parent frame must actually be a frame. You are currently passing ClassIcons, which is a table, not a frame. Similarly, you cannot use SetPoint to position things relative to a table, because a table does not have any position or of the other "physical" attributes a frame has.

The easiest solution would be to make ClassIcons a frame, like the combo point holder is:

local noop = function() return end

lib.genHoly = function(self)
	if select(2, UnitClass("player")) ~= "PALADIN" then return end

	local ClassIcons = CreateFrame("Frame", nil, self)
	ClassIcons:SetPoint("BOTTOMLEFT", self, "TOPLEFT", 0, 7)
	ClassIcons:SetSize(140, 20) -- 5 icons * 20 width + 4 spaces * 10 width

	-- Optional, to match the combo points:
	bars:SetBackdrop(backdrop)
	bars:SetBackdropBorderColor(0,0,0,0)
	bars:SetBackdropColor(0,0,0,0)

	for i = 1, 5 do
		local Icon = CreateFrame("StatusBar", nil, ClassIcons)
		Icon:SetSize(20, 20)

		-- You do not need a SetPoint line here, because you have some
		-- later that just override the one that was here.	

		Icon:SetStatusBarTexture(config.statusbar_texture)
		Icon:GetStatusBarTexture():SetHorizTile(false)

		Icon:SetBackdrop(backdrop)
		Icon:SetBackdropColor(0,0,0,1)

		-- Map the method oUF tries to call to one that actually exists:
		Icon.SetVertexColor = noop

		if i == 1 then
			Icon:SetPoint("LEFT", ClassIcons)
		else
			Icon:SetPoint("LEFT", ClassIcons[i-1], "RIGHT", 10, 0)
		end
		ClassIcons[i] = Icon
	end

	ClassIcons.PostUpdate = HolyPostUpdate
	self.ClassIcons = ClassIcons
end